1. Field of the Invention
The present invention relates to a tone signal generator utilizing ancillary memories for an electronic musical instrument system reading out waveform data from the ancillary memories to generate a tone signal based on the read out waveform data. More particularly, the present invention relates to a tone signal generator utilizing the ancillary memories as a double buffer memory in order to generate a sound signal recorded in the natural world, a sound signal electronically synthesized, etc. as a continuous tone signal for a long period of time.
2. Description of the Prior Art
In Japanese Patent Application Laid-Open No. Sho51-130211, there is disclosed a tone signal generator for an electronic musical instrument having a source memory for beforehand storing several sets of waveform data which represent a cycle of waveform respectively, first and second read/write memories for storing waveform data which represent a half cycle of waveform and an address counter for designating addresses of both the read/write memories, wherein under address designation of the address counter each waveform data stored in the source memory are written into the read/write memories every predetermined time interval and the written waveform data are repeatedly and alternately read out from the read/write memories in order to generate a tone signal. The tone signal generator further comprises a calculation circuit for modifying the waveform data stored in the read/write memories, the modified waveform data are also written into the read/write memories under address designation of the address counter. In the tone signal generator, however, writing and reading operations are controlled synchronously by the single address counter. This results in the difficulty of designing a writing operation portion and a reading operation portion independently. Additionally, in the tone signal generator, a source memory does not store a continuous waveform data for a long period of time. As a result, a generated tone signal becomes monotonous.